This invention relates to a method of selectively adapting an electronic control unit for use in internal combustion engines, and more particularly to a method of this kind which enables the electronic control unit to be applied both to engines equipped with automatic transmissions and ones equipped with manual transmissions, without changing the structure of input ports, input circuits, etc. of the electronic control unit.
There is conventionally known an electronic control unit for controlling the operation of internal combustion engines, which is adaptable both to an engine installed in a vehicle equipped with an automatic transmission (hereinafter merely called "the AT vehicle") and one equipped with a manual transmission (hereinafter merely called "the MT vehicle"), in such a manner that control data applied for controlling the operation of an engine in the AT vehicle and control data applied for controlling the operation of an engine in the MT vehicle are both stored in storage means in the electronic control unit, and one of the two kinds of control data is selected for use, which corresponds to the type of a transmission associated with an engine to be controlled, thereby enhancing the mass productivity of the electronic control unit.
According to such a versatile type electronic control unit, in order to adapt the electronic control unit to the AT vehicle or to the MT vehicle, a changeover switch, the position of which determines the control data to be selected, is connected to one of input ports of a central processing unit (hereinafter called "the CPU") to supply a signal indicative of the position assumed by the changeover switch to the CPU, and the central processing unit selects one of the two kinds of control data that corresponds to the position assumed by the changeover switch.
The conventional electronic control unit therefore requires one of the input ports which are limited in number to be exclusively used for connection with the changeover switch, thus imposing a further limitation upon the number of input ports that can be used for inputting other engine operating parameters, etc. to the CPU.